Genes expressed in the male reproductive system exhibit rapid evolutionary change and encode products that underlie striking, fitness-related phenotypes. Despite this, they have been characterised in detail in relatively few species. We report here an initial characterisation of the genes expressed in the male reproductive accessory glands of the Mediterranean Fruit Fly (Ceratitis capitata). We describe 13 independent expressed sequence tags (ESTs), of which 9 showed significant homology to known sequences and of which 4 represented novel sequences. The evidence suggests that our transcripts are not homologues of genes encoding known accessory gland proteins (Acps) in Drosophila melanogaster, but that they do encode proteins that fall into known functional categories for Acps (e.g. proteases, lipases, cysteine-rich secretory proteins [CRISPs]). Our results are consistent with the finding that among Acps there is considerable evolutionary lability at the sequence level, but evolutionary constraint at the functional level. The results highlight the extraordinary diversity of male reproductive genes.